1. Field of the Invention
The invention relates to a tapered roller bearing, and in particular, to a tapered roller bearing that stores a lubricant in a space where tapered rollers roll.
2. Description of the Related Art
A tapered roller bearing includes an outer ring, an inner ring, a plurality of tapered rollers, and a cage. The tapered rollers are arranged such that an axis of each roller around which the roller rolls is inclined with respect to an axis of the tapered roller bearing. A large-diameter bottom face (hereinafter also referred to as a roller large end face) of the tapered roller is arranged outward of a small-diameter bottom face (hereinafter also referred to as a roller small end face) in a radial direction of the bearing.
The tapered roller bearing characteristically needs to offer enhanced resistance to seizure between the roller large end faces of the tapered rollers and a surface of the inner ring that contacts the roller large end faces (hereinafter referred to as a cone back face rib surface) and to suppress wear of a pocket surface of the cage of the tapered roller bearing. As such a tapered roller bearing, a tapered roller bearing is known in which a lubricant holding member is attached to the outer ring so that a lubricant can be stored in a space between the lubricant holding member and the outer ring (for example, Japanese Patent Application Publication No. 2008-057791 (JP 2008-057791 A) and Japanese Patent Application Publication No. 2008-223891 (JP 2008-223891 A)).
In the tapered roller bearing, the lubricant holding member is integrally attached to the outer ring. In contrast, the cage rotates with respect to the outer ring when the bearing rotates. Thus, when the cage and the lubricant holding member are in contact with each other, friction may occur between the cage and the lubricant holding member to affect a rotating operation of the bearing.
In general, the cage is formed of metal and manufactured by press molding, and thus, changing the shape of the cage is difficult. Thus, to arrange the cage and the lubricant holding member so as to avoid contact between the cage and the lubricant holding member, the axial dimension of the lubricant holding member needs to be sufficiently large to form a clearance between the lubricant holding member and the cage.
On the other hand, there has been a demand to downsize the tapered roller bearing in order to increase the degree of freedom of installation of the tapered roller bearing. Therefore, the lubricant holding member is preferably downsized.